Why Hasn't first gone Brushless?
 

Hello all,
First post here, So I'll introduce myself. My name is Ben White of team 87- if any of you were at the granite state regional or Philadelphia regional- i was the tall black guy on drive team.. Kind of hard to miss me:p. I am team 87's hardware man and have a question


My question to you is why FIRST has not gone to brushless motors and speed controllers over the CIM motors, 884's and jaguars?
Brushless motors are loads more efficient, make more torque, and can be purchased with different winding configurations for different kv and Kt values.(rpm per volt and torque per amp).

For any of you that run hobby grade RC cars, you have seen the advantages of brushless motors. you get longer runtime, more power and the motors are less temperamental when under load.



What I would like to see is that first legalizes brushless motors and speed controls... yes they are expensive but they have their advantages.

Re: Why Hasn't first gone Brushless?
 

You just provided the answer to your own question.


-dave




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Re: Why Hasn't first gone Brushless?
 

I'm going to go out on a limb and say... cost.

FIRST would have to provide the motors to all the teams in the KoP.
The 2.5" CIMs are approximately 337 Watt motors, and cost $28 individually from Banebots. This brushless motor with a peak wattage of 350 costs nearly 3x as much.

Edit: beat to it

Re: Why Hasn't first gone Brushless?
 

Assuming that the rules allowed it, what motor driver and motors would you use? Do you have any specific parts to recommend? Along Dave's lines, could you also list the $$$ factor?

The powers that be at FIRST are reasonable, but they respond much better to "It would be cool to do X, and here is how we can reasonably achieve it" than "Why aren't you doing X?".

Re: Why Hasn't first gone Brushless?
 

Well if they just legalized them as in let teams use them without putting them in kits... you would have teams with ridiculous advantages over any team who can't afford the price tag on even a small brushless motor. An Axi-2208 which is a comparable replacement for a motor a tough smaller than like the Banebots.. is about $75. Not to mention the price of the speed controllers.

And FIRST can't afford to put them in the kits. I'm sure they can pick up CIMs surplus for under $10.. nowhere can you pick up brushless cheap for surplus so that's why they can't just include it in the kit. They cost a lot in general.

Re: Why Hasn't first gone Brushless?
 

I see the Lavery family suffers from cost consciousness (as does the Forbes family)

Efficiency is great, if you can afford it. Usually we can't.

Re: Why Hasn't first gone Brushless?
 

FIRST may go brushless for a water game. ;)

Re: Why Hasn't first gone Brushless?
 

If that were true we would have brushless motors this year.

Re: Why Hasn't first gone Brushless?
 

Yeah, and with the fairly high weight limit and short matches, there's really no design crunch to move to a more expensive/efficient motor. Although you're right, FIRST doesn't even allow teams to use brush motors that don't come in the kit; if they let teams buy comparable brushless you would start to see even more of a gap between well to do and not so well to do teams.


You make a very interesting point about the motor coefficients, too. Moving to brusheless opens up a lot of design parameters to which students don't currently have much exposure. Picking motors based on their performance and fit with your design becomes much more complicated and interesting.

Re: Why Hasn't first gone Brushless?
 

The jags and victors will work with most any brushed DC motor that is with in the power specs. With ECM motors the controller needs to be designed for the motor and that means more money and less flexibility. First can include any 12volt brushed motor they want to. With the NI C-Rio and the availability of CAN and LIN busses, First could include a brushless motor in the future. The automotive industry is going toward intelligent modules. In the future First could find a deal on surplus window, light, seat position, moon roof, rear hatch or other modules that use ECM motors. Then it would be up to Ni and WPI to write the interface for us.

Re: Why Hasn't first gone Brushless?
 

Luminary Micro makes reference motor controller kits for brushless, stepper, and AC induction motors. If FIRST wanted to foray into other motor types, I'm sure they could work it out.

I'd rather get stepper motors before FIRST went brushless.

Re: Why Hasn't first gone Brushless?
 

I agree. This would be a better next step ;)

Re: Why Hasn't first gone Brushless?
 

Some stepper motors would be pretty sweat. Holding toque for a stepper motor is really nice..

Re: Why Hasn't first gone Brushless?
 

All our robots would look better in those little Canadian hats, with or without stepper motors. http://en.wikipedia.org/wiki/Tuque

(EDIT: Kingof1337 made an innocent typing error that generated something even better. I had no intention to make fun of anyone. My screen name is an example of my own ability to miptyse something.)

(EDITED AGAIN: It's an Internet rule - predating the WWW - that all criticisms of someone else's grammar or splelling should contain a similar misteak.)

Re: Why Hasn't first gone Brushless?
 

As is your response. :)

-dave

Re: Why Hasn't first gone Brushless?
 

I understand the cost Of it, not saying that they would need to be supplied in the KOP, but why not make them legal. I dont see anyone complaining about the cost of the cRio's....:rolleyes:
They aren't cheap either but everyone benefits from them

At only 337watts the cim motor is not THAT powerful of a motor.. The Brushless system of my Brushless rc car puts out more then double that. If you wanted something comparable to the cim in brushless form, it would be half the size and the only thing needed to use it are shaft adapters which can easily be made.

As for price, Not every system you look at is that expensive
http://www.hobbycity.com/hobbycity/s...idProduct=7392
Take for example, that motor 30 bucks, and rated for double the power and more then the cim.

Before everyone jumps to conclusions about price and effectiveness, do some research- things are always not as they seem.

Re: Why Hasn't first gone Brushless?
 

Historically, FIRST hasn't allowed non-kit motors. The lone exceptions in recent years have been for the CIM motors, where two were provided with the kit (and a total of four would be legal). I'm sure someone with more time under their belt can expand on the idea behind that decision.

The CIM motor is powerful enough to power nearly any manipulator a team could need, and more than powerful enough to tackle a person (or whack them in the chin--don't ask). If it's enough to let us send a robot screaming downfield at upwards of 10 feet per second, do we really need more power? Also, never rule out the importance of those shaft adapters--someone has to make them, and that takes money.

Also, perhaps someone can enlighten me about this: how durable are these motors compared with motors currently in the kit? Sure, they might be more powerful--but that's no good if they burn up when stalled for a tenth of a second, or are particularly intolerant of abuse during assembly and testing. I missed out on the brushless era in R/C trucks (I quit racing when I went to college), so I'm unfamiliar with the state of the art these days.

Re: Why Hasn't first gone Brushless?
 

The motors provided in the KOP's are fine and easy enough to deal with. The fact that the motors and accessories are under so much restriction is a plus in my opinion because it's one elss thing that a team has to worry about. We just need to learn how to deal with the restrictions and constraints. Plus, it makes things much more fun and interesting :)

Re: Why Hasn't first gone Brushless?
 

The problem then is, as pointed out by multiple people earlier in the thread, it widens the gap between the "have" and "have not" teams. Motors have typically been (aside of additional CIMs and spares) provided in the KoP and teams have only been allowed to use the provided KoP motors. This ensures equality, as well as helps teams learn how to effectively use provided resources.

Nobody hear said that the CIM is that powerful, but it is powerful enough for virtually any FIRST application. Even in carpeted games, a two-CIM per side drivetrain through a transmission can produce more than enough force to break traction wheels loose from the floor. Once you surpass your static friction, additional force doesn't do much good.

The motor alone isn't the only thing that adds cost to a brushless motor. Teams would then need to buy addition speed controllers (though usually in the same ballpark as jaguars and victors) for their new non-KoP motors.

What voltage is the motor you linked to designed to run at? The one I found was designed for 10.5 and put out comparable numbers to a CIM, although was significantly more expensive.

Re: Why Hasn't first gone Brushless?
 

here is a similar question.

why hasnt FIRST used 12v 18Ah lipo batteries?

Re: Why Hasn't first gone Brushless?
 

Fire = bad

-Greg

Re: Why Hasn't first gone Brushless?
 

Please direct me to some 12V 18Ah LiFePO4 batteries that aren't cost prohibitive. Note our discharge rates!

Re: Why Hasn't first gone Brushless?
 

i noticed someone mention that they would to like to see stepper motors before brushless motors. it was my understanding that brushless motors were just stepper motors with fewer steps, could someone enlighten me if i am wrong

Re: Why Hasn't first gone Brushless?
 

indeed (:

id like said batteries too, ive been looking for some cheaper-than-an-arm-and-a-leg lipo batteries too ):

Re: Why Hasn't first gone Brushless?
 

Yes stepper motors are very closely related to Brushless motors, Both use digital current switching over brushes and commutator. Without the brushes, there is nothing that can wear out in a brushless motor also.


For those who dont know what a brushless(non outrunner) motor is, here is a really breif look at them. In the Layest(new word?) of layman's terms a brushless motor is a brushed motor flipped inside-out. the windings usually found on a brushed motor's armature are replaced by a permanent magnet in the brushless motor. Windings(stator) in a brushless motor are bonded to the inside of the motor can.

Since the current switching of Brushless motors is handled by the speed controller, the commutator, brushes and all associated components arent used in them.. the only moving part is the rotor. Brushless motors are 99% maintenece free.


A note on efficiency from an Industry Leader, Castle Creations

Re: Why Hasn't first gone Brushless?
 

yea ithink i would say cost too because brushless is a lot
and frist is a non profit ..

Re: Why Hasn't first gone Brushless?
 

Ben,
All things being considered, the brushed motors are the best choice for our competition. Maintenance free is not a problem for this competition since the service life is measured in hours not months. Not one team I am aware of has ever failed a motor due to brush wear or bad bearings other than those over stressed by bad design. Controllers for brushless motors tend to be more complex and vary with the design of the motor, i.e. how many poles/phases need to be controlled. Brushless motors have a bad tendency to lag under heavy loads. Brushless motors tend to be better for fixed applications like fans, video recorder head wheels and other applications that require some sort of phase lock or rotation lock. Stepper motors can be a better choice for some of our applications but again controllers become very complex. All of these motors reguire some form of feedback to operate and change speed and so control then lies outside the ability of most rookies and those teams with few mentors. IMHO, brushed motors and speed controllers still give us the most level playing field and are the easiest to implement for the majority of teams.

Re: Why Hasn't first gone Brushless?
 

as a owner of over $2000 of brushless motors, i dont think its a good idea for a few reasons

1. Need to pay MUCH more attention to gearing/heat/ etc. 90% of brushlesss motors need to be kept at about 45k RPM. Close monitoring of motor and ESC temperatures must be read and translated.

2. Cost. Yes there are $30 brushless motors, but those tend to have magnet separation. the FIEGO XL is a $60 motor but IMHO the only motor worth it is the NEU series motors at $300 each! Either way, MUCH more expensive. The economy is not in good shape, FIRST needs to stay afloat!

Lipo batteries ARE THE WAY TO GO!!! I run 12s setups giving more that 48V of power and iv never had a problem....but that dosnt mean someone that dosent know what they are doing wont catch one on fire because they didn't read the instructions...:ahh:
NOT TO MENTION the cost of a LIPO charger?! Mine costs $270....and people have to learn how to use em, balancer taps are a mysterious thing for anyone who have never used em:o

Basically im saying YES it would be AWESOME if first went LIPO and BRUSHLESS, but it dosent make sense right now:)

Re: Why Hasn't first gone Brushless?
 

Stepper motors would be SWEET. Position control without having to install yet another encoder and write yet another PID loop?

Sign me up.

Re: Why Hasn't first gone Brushless?
 

Andrew,
LIPO batteries will catch fire in the hands of teams who regularly damage the AGM cells we currently use. Fire on the field is not something I want to be a part of.
Jared,
Stepping motors and feedback are not mutually exclusive. You have to know where you are in order to control where you want to be.

Re: Why Hasn't first gone Brushless?
 

The cost-based argument against brushless motors is quite compelling, but how about the possibility of a single brushless motor (and appropriate control devices). Might there be some brushless motor that would fill a nice niche for FIRST robots; perhaps higher torque applications without needing as much gearing?

Re: Why Hasn't first gone Brushless?
 

Being able to use the CAN port on the new motor controllers should help *a little bit*

Re: Why Hasn't first gone Brushless?
 

True, but for small loads, counting steps from a known reference position is often just as good as using feedback.

Re: Why Hasn't first gone Brushless?
 

Brushless motors actually perform better under low loads (they don't have huge advantages over brushed motors for high load tasks), so a high torque application with low gearing is the opposite of what you'd want to use them for. That's why you typically see brushless motors in high-speed, lower-load applications such as hard drives, cd players, or RC airplane props.

The ideal applications on an FRC bot for brushless motors would be shooting wheels (best application), intake rollers, and some drive systems (or similar).

Re: Why Hasn't first gone Brushless?
 

I know how you could be solely responsible for getting brushless in FRC.

Simply get a brushless motor you would like to use, the speed controller for it that is compatible with our system, then buy, oh, 10,000 or so. Donate to FIRST, it may happen.

Other than that, sorry.

Separate from that, I've used brushless motors in combat robots before. FIRST shouldn't have brushless for two reasons; one, the drive is plenty, plenty powerful enough, and secondly teams would be destroying them constantly.

Re: Why Hasn't first gone Brushless?
 

One good thing about brushless is that they can come sensored, and extra encoders/sensors are not needed as the motor, tied with programming can precisely know its rotation or degree.

The brushed motors seen in these robots do not go through as many revolution in their lifetime as their similar counterparts in RC cars or in factory machines. These motors do not get to the point of maintenance that brushed motors usually require like new brushes or having the commutator cut. The maintenance of brushless motors in this case is unnecessary then.

Like Adam said, the motors we are given already are more than enough powerwise and efficiency wise for 2 minute matches, if designed properly. Races usually go at least 5 minutes up to 10 or even 20 minutes require brushless motors to last the longest and lipo batteries with huge capacities that do not start dipping until the last 1 or 2 minutes of the race.

These are smaller reasons of why they are not necessarily crucial to being in the KOP, but also because of costs. Brushed speed controller vs brushless and having 10,000+ motors. That would be a very generous donation as each motor would be at least twice the cost of a cim motor.

But to give brushless a fighting chance, motors and speed controllers have been getting cheaper. They could someday be cheap enough to make their way into the kits.

Re: Why Hasn't first gone Brushless?
 

Most brushless motors are sensor less and that leads to another reason why not to use them. Sensorless motors are harder to start.

Re: Why Hasn't first gone Brushless?
 

Cogging is what your thinking about, and this goes to cost again...low cost motors and controllers tend to have SEVERE cogging issues at low throttle

NEU 6pole motor with a MGM or Caste Creation MM or MMM can compete with many sensored setups. If i can get a 1500kv sensor less BL motor to go 0.2 mph on a crawler....Completely unrelated...i honstly believe sensorless BL motors will be the way...they are already proving to kick more butt on the tracks:D

Re: Why Hasn't first gone Brushless?
 

That isn't what I was thinking of. Sensorless motor controllers work by measuring zero crossing point of the back EMF. If the motor isn't moving there is no back EMF which means you are essentially driving blind as to what position the motor to the windings.

Re: Why Hasn't first gone Brushless?
 

Personally, what I'd like is 3-phase motors. If you chose a motor within the correct speed and torque range, you need no gearing whatsoever, and can actually direct drive every wheel with its own motor. (crab drive with traction control, anyone?) There would be no need for a CVT.
However, there are some good reasons we haven't done this yet:

Luminary micro doesn't make a polyphase motor controller. While we could theoretically use 3 AC motor controllers to control torque, we would still require a variable-frequency 3-phase inverter to control speed.

AC signals can't be treated the same as DC signals. Calculating wattage and resistance is different, and you have to account for inductive reactance. Also, FIRST wiring standards would have to increase greatly to deal with 240v power.

I haven't investigated it, but I'm pretty sure 3-phase motors of a usable scale to us are mainly used on milling machines, and thus are upwards of $150 for the motor alone. This definitely isn't something FIRST can get for free.


Anyways, I figured I'd add my thoughts to the wish-list.

Re: Why Hasn't first gone Brushless?
 

Unless everybody drags 120VAC extension cords all over the place, I don't think we'll be seeing 3-phase any time soon.

Re: Why Hasn't first gone Brushless?
 

Marshall,
Three phase (or polyphase) motors operate in relation to the way they are wound and the input frequency. Their greatest torque is at the speed for which they are designed. There is a distinct relationship between the number of windings/poles and the operation of the motor. When these motors are manipulated for speed, the controllers are adjusting frequency. The controller is essentially a large power amplifier. And they don't change speed quickly. In general when a person speaks of three phase motors, they are referring to power line operated devices used in locations where three phase power is available.

Re: Why Hasn't first gone Brushless?
 

There are so many problems with using 3-phase motors on FRC robots. Not the least of which is safety, having 120/240V around. I'm sure we'd all love to have kids wiring a high voltage system, which could rather easily kill them. I'm also not too familiar with inverters, but we would either need something that converts from 12VDC or have some way to store higher voltages (and then convert those to AC) on the robot, or have power lines leading to the robot (can you say "accident waiting to happen"?)

In my opinion, the safest, and most logical thing to do for FRC robots is to use some form of DC motors. Right now, brushed motors are being used due to logistics, and availability/price. Maybe, sometime in the (hopefully near) future, brushless motors could be used.

Re: Why Hasn't first gone Brushless?
 

While we're on the topic of allowable actuators, I would really like if we were allowed to use electric solenoid actuators. There are so many applications (dog-style shifters, brakes, clutches, latches, etc.) where I'd love to be able to eschew a full-size motor or piston, and where a servo just doesn't cut it.

Re: Why Hasn't first gone Brushless?
 

I wholeheartedly agree. There are a variety of great solenoids that eams could put to great use if allowed. Additionally, electrically operated clutches would be nice.

Re: Why Hasn't first gone Brushless?
 

I was thinking the same thing a few weeks back. Do you know of any specific models that might fit?


On the AC motor "topic", thanks for the chuckles. Greg pointed out that it would make designing the PD a bit easier - just get a plug strip! Now we just need to find 3 phase AC batteries...

Re: Why Hasn't first gone Brushless?
 

Eric,

I'm sure that Al will know much more on the subject than I do, but I have used models from Pontiac Coil that are sold on DigiKey. Looking at DigiKey, most are in the $20-40 range and are 12V, .5-1.5" stroke, and offer holding torque on the order of a few to tens of ounces.

Re: Why Hasn't first gone Brushless?
 

Let alone three-phase power on FRC robots, I just want [480v] three-phase power in my house!

There are tons of used (still in good condition) three-phase Bridgeport manual milling machines on eBay all the time within driving distance that are selling for $2k-$5k. Some even come with DROs! Who wouldn't want a full size manual mill at their house? :D

But the electric companies are like you're residential, grumble, grumble, single-phase 240v only, grumble, grumble, just use a rotary phase-converter, grumble, grumble.

Re: Why Hasn't first gone Brushless?
 

I can't wait for the day when tool changers are a reasonable option on an FRC robot.